Experimental Progress Zebrafish visual behaviors: We are preparing a manuscript describing the combinatorial coding properties of neurons in the larval zebrafish optic tectum. The collection of large scale electron microscopy data from a functionally characterized tectum is underway. Neurogenesis in the olfactory bulb: We are preparing a manuscript describing the connectivity patterns between adult born neurons and projection neurons in the mouse olfactory bulb using a combination of optogenetic and electrophysiological approaches. We are also preparing a manuscript describing a novel method to allow penetration of antibodies into thick tissue sections with minimal disruption to tissue ultrastructure. This method has been used to triple immunohistochemically label periglomerular cells in the mouse olfactory bulb. We completed the collection of a large electron microscopy of this tissue and are in the process of analyzing the dense connectivity patterns of periglomerular cells in olfactory bulb glomeruli. EM analysis of retinal circuitry: A collaboration with the labs of Dr. Rob Smith and Dr. Jeff Diamond led to a publication that appeared in Nature in 2016. In this study we identified a species-specific wiring difference in the direction-selective circuitry of mice and rabbits. This wiring pattern difference compensates for their substantially different eye diameters and allows the two species to encode similar angular velocities in visual space. Technical Progress Development of custom serial-block face microtome: An application was filed to license our serial block-face microtome and a licensing agreement is pending. 3D EM data analysis: We have pursued two avenues to aid the automated analysis of 3D EM data. On the experimental side, we conducted a study examining the benefits of preserving the extracellular space during chemical tissue fixation that is normally lost. We have confirmed that the preservation of extracellular space improves the automated segmentation of 2D and 3D EM volumes. A manuscript describing this method was published in Elife in 2015. On the data analysis side, we have scaled up our machine learning-based data analysis pipeline to be able to segment terabyte-scale datasets. We are currently using the pipeline to analyze the recently acquired mouse olfactory bulb dataset. Web based Proofreading Tool: Our web based EM segmentation proofreading tool is online and externally accessible. We added a tutorial to demonstrate how to use the site. We are using the tool to accumulate more training data for the neural networks.